1.3 Measurement Scientists work with very large or very small numbers Scientific notation uses a shortcut to avoid writing out all the zeros Scientific notation is a way of expressing a value as a product of a number between 1 and 10 and a power of 10 e.g. 3 x 108

International System of Units (SI) There are 7 metric units known as base units: meter (m) – length kilogram (kg) – mass kelvin (K) – temperature second (s) – time mole (mol) – amount of a substance ampere (A) – electric current candela (cd) – luminous intensity

Derived Units Derived units are made from combinations of base units. Density is a derived unit e.g. Density = mass ÷ volume

Writing Quantities Quantities are seldom convenient to write out A more compact way is to use a metric prefix A prefix indicates how many times a unit should be multiplied or divided by 10

Precision Precision is an assessment of how exact a measurement is. Significant figures are all the digits that are known in a measurement, plus the last digit that is estimated. The fewer the significant figures, the less precise the measurement is. A calculated answer is limited by the least precise measurement used in the calculation Accuracy is the closeness of a measurement to the actual value of what is being assessed.